Long runs of electrical conduit are used to contain and protect one or more electrical wires in areas where the wires need the protection such conduit offers. The conduit is typically formed of sections joined by couplings and often includes bends along the conduit length. The conduit usually extends between junction boxes where wires contained within the conduit are electrically connected to components for transmission of electricity.
In electrical installations, the conduit is first assembled between junction boxes before the wires are then pulled through the conduit length. While various powered pullers are used for this purpose, it is often a difficult process to pull the wire through the conduit, especially if there are many bends along the conduit length. It is not unusual that the puller cords break, leaving a partially pulled wire end very difficult to access within the conduit length.
Lubricants have been developed to decrease the frictional resistance to movement of the wires through conduit. This lubricant is similar in consistency to automotive grease and is typically deposited into the conduit at the upstream end from which the wires are to be pulled.
The lubricant is certainly beneficial to the pulling process, but often rubs off the wire long before the pulled wire end reaches its destination. Thus the beneficial effects of the lubricant is short lived and the difficulty in pulling the wire reoccurs.
Another problem faced by electricians applying lubricant to conduit ends is the mess caused by feeding the lubricant, usually by hand, into the conduit. Much of the lubricant typically spills over the end of the conduit and into the associated junction box where it must later be cleaned up. This process is time consuming and therefor expensive to the electrical contractor.
The above problems are addressed to limited degree in U.S. Pat. No. 4,688,762 to DeBeradinis. This patent discloses a method for lubricating conduit in which couplings along the conduit length are provided with removable plugs. The plugs are removable to enable insertion of lubricant at points along the conduit length.
While this method serves to provide access for lubricant along the conduit length, the plugs must first be removed, and then replaced after the lubricant is injected. This is a time consuming task and can take longer to accomplish than the original method of simply manually inserting the lubricant at the upstream end of the conduit.
Further, removable plugs require that the electrician or helper remember to replace the plugs following removal. If a plug is not replaced, the interior of the conduit and contents are exposed to the very hazards the conduit is used to protect against.
A further problem is that the plugs must be situated on the upward side of the conduit to avoid the lubricant falling or draining back out. This becomes a significant problem, especially in confined areas. Such confined areas also restrict use of the tools required to remove and replace the plugs.
Another attempted solution to the problem is addressed by Salerno et al in U.S. Pat. No. 3,605,947. Here, hollow frangible disks filled with lubricant are placed within couplings between adjacent ends of joined conduit sections. The intent was to burst the disks, freeing the lubricant as the wires are drawn through the conduit. However, the disks themselves present obstructions to passage of the puller cord, as well as the broken membranes previously used to contain the lubricant.
Also, most pullers make use of air pressure to initially push a ball or other object of similar diameter to the conduit to "snake" an attached puller cord through the conduit. This process normally requires that the conduit be free of obstruction. Otherwise air pressure would build within the conduit between the ball and the first frangible disk as the ball progresses along the conduit. Thus progressively increasing air pressure becomes required to drive the ball ahead.
A ball encountering a disk would either be stopped or would burst the disk. The lubricant from a burst disk would then hinder further passage of the ball, being pushed ahead of the ball to the next disk where the same difficulty would again occur.
The present invention includes as an objective provision of a self closing lubricating fitting on a conduit coupling that facilitates quick injection of lubricant along the conduit interior at any angle.
Another objective is to provide such a coupling and fitting that leaves the interior of the conduit unobstructed and thereby facilitates free normal passage of puller cord and wire therethrough.
A still further objective is to provide a process for lubricating the interior of electrical conduits in a fast an effective manner, while the conduit remains substantially closed except for the open ends thereof.